The present invention relates to fuel delivery systems for engines and, more particularly, for aircraft engines.
An important focus of improvements to aircraft engine operation concerns the reduction of greenhouse gas emissions due to fuel consumption. Whilst this is a concern for the whole life-cycle of aircraft engines, there is also a more specific consideration of local air quality (LAQ) in the vicinity of airports.
U.S. Pat. No. 8,311,686B discloses a method for assessing engine emissions and/or noise at a collection of ground-based monitoring stations, and presenting the results of that assessment to pilots such that they may determine and implement appropriate actions to minimise the emissions/noise at each of the ground stations. The assessment makes use of information such as aircraft location/altitude relative to each ground station, wind-speed/direction, and engine operation parameters influencing the quantity of emissions actually produced.
However U.S. Pat. No. 8,311,686B does not provide any executive action or decisions for ways to actually reduce emissions but rather requires human interpretation of the output information in order to decide what action may be most appropriate.
It is known in a general sense that the use of alternative aviation fuels can enable reduced levels of emissions from engines. Currently, alternative fuels (particularly biofuels) suffer a very significant price disadvantage in comparison with standard kerosene, and are in short supply. There are also technical limitations which prevent in many cases the complete substitution of kerosene with an alternative aircraft fuel and so, if such alternative fuels are used at all, they are typically supplied to aircraft in a predetermined blend comprising a high percentage of kerosene (representing the majority component within the blended fuel) and an alternative fuel (representing the minority component within the blended fuel).
The relative proportions of alternative fuel and kerosene within the blended fuel composition are determined by such factors as the availability and price of alternative fuel at the aircraft's departure airport, and the attitude of the aircraft operator to the use of alternative fuels which may cost significantly more per liter than standard kerosene. Regulatory limits or technical constraints may also place an upper bound on the proportion of alternative fuel that may be incorporated within the fuel blend.
It is an aim of the present invention to provide an engine fuel delivery system that can provide for a reduction in one or more environmental impact concerns.